Preheat air fryer to 400°F for 3 minutes.
Peel butternut squash and cut into 1-inch cubes.
Place the squash cubes in a mixing bowl and toss with olive oil to coat evenly.
Sprinkle on onion powder, garlic powder, sweet paprika, cayenne, kosher salt, and optional brown sugar; toss until all pieces are coated.
Arrange the squash in a single layer in the preheated air fryer basket; do not overcrowd.
Air fry at 400°F for 10 minutes without opening the basket.
Shake the basket to flip the pieces for even browning.
Air fry for another 10 minutes, until edges are caramelized and the thickest pieces are fork-tender.
Adjust time as needed based on cube size or air fryer model (check at 17 minutes if your unit runs hot).
Serve immediately.